js_runtime: Split _asyncHelper into separate functions

pkg/compiler/lib/src/js_backend/backend.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library js_backend.backend;
 
 import '../common.dart';
 import '../common/backend_api.dart'
     show ForeignResolver, NativeRegistry, ImpactTransformer;
 import '../common/codegen.dart' show CodegenImpact, CodegenWorkItem;
@@ skipping 1267 matching lines @@
   /// supported by the backend.
   bool enableCodegenWithErrorsIfSupported(Spannable node) => true;
 
   jsAst.Expression rewriteAsync(
       FunctionElement element, jsAst.Expression code) {
     AsyncRewriterBase rewriter = null;
     jsAst.Name name = namer.methodPropertyName(element);
     switch (element.asyncMarker) {
       case AsyncMarker.ASYNC:
         rewriter = new AsyncRewriter(reporter, element,
-            asyncHelper:
-                emitter.staticFunctionAccess(commonElements.asyncHelper),
+            asyncStart:
+                emitter.staticFunctionAccess(commonElements.asyncHelperStart),
+            asyncAwait:
+                emitter.staticFunctionAccess(commonElements.asyncHelperAwait),
+            asyncReturn:
+                emitter.staticFunctionAccess(commonElements.asyncHelperReturn),
+            asyncRethrow:
+                emitter.staticFunctionAccess(commonElements.asyncHelperRethrow),
             wrapBody: emitter.staticFunctionAccess(commonElements.wrapBody),
             completerFactory: emitter
                 .staticFunctionAccess(commonElements.syncCompleterConstructor),
             safeVariableName: namer.safeVariablePrefixForAsyncRewrite,
             bodyName: namer.deriveAsyncBodyName(name));
         break;
       case AsyncMarker.SYNC_STAR:
         rewriter = new SyncStarRewriter(reporter, element,
             endOfIteration:
                 emitter.staticFunctionAccess(commonElements.endOfIteration),
@@ skipping 150 matching lines @@
 
   bool canUseAliasedSuperMember(MemberEntity member, Selector selector) {
     return !selector.isGetter;
   }
 
   /// Returns `true` if [member] is called from a subclass via `super`.
   bool isAliasedSuperMember(MemberEntity member) {
     return _aliasedSuperMembers.contains(member);
   }
 }